1. Field of the Invention
The present invention relates to a laser optical apparatus, and more particularly, to a laser optical apparatus, which removes speckles from a screen and improves light efficiency so as to display a bright and clear image having excellent picture quality.
2. Discussion of the Related Art
Generally, display units have been developed towards light-weight, thin and large-screen trends, and been pursued to display an image having high-luminance, high-definition, and high-contrast.
Due to the recent development of a projection display technique, there have been significant developments towards high-luminance and high-contrast characteristics of display units. Particularly, a projection display unit for displaying an image on a large-sized screen by enlarging the image using a display system for forming the large-sized screen has been proposed.
FIG. 1 illustrates a projection display unit using a lamp as a light source. As shown in FIG. 1, light emitted from a lamp 10 is concentrated on one side by a reflecting mirror 20, and the light concentrated by the reflecting mirror 20 is irradiated onto an image display unit, such as an LCD panel 30a. The LCD panel 30a adjusts transmittance of the light, thereby displaying an image. The image is enlarged and projected by a projection unit 40, and is formed on a screen 50. A user at the front or rear side of the screen 50 sees the image formed on screen 50.
Conventionally, a lamp was used as the light source of the above projection display unit. Recently, a laser projection display unit using a laser as a light source has been developed.
The laser projection display unit using the laser as the light source is advantageous in that an obtained image is clear and has a broad range of nearly solid colors. Further, the obtained image of laser projection display unit has a high contrast, thereby being clear.
FIGS. 2 and 3 respectively illustrate laser projection display units using a laser as a light source.
As shown in FIG. 2, a laser projection display unit uses a laser 60 instead of the lamp as a light source. An illuminating unit 70 irradiates a laser beam emitted from the laser 60 on a display panel 30b. The display panel 30b adjusts the quantity of the beam according to an electric signal, and displays an image. An image projecting unit 40 projects the image on a screen 50 so that the image is enlarged and displayed on the screen 50.
As shown in FIG. 3, another laser projection display unit uses the laser 60 as a light source. The illuminating unit 70 concentrate a laser beam emitted from the laser 60 on an Acoustic Optic Modulator (AOM) 80. The AOM 80 adjusts the quantity of the transmitted beam according to an electric signal in connection with an image signal.
The laser beam adjusted by the AOM 80 travels to a polygonal mirror 90. Here, the polygonal mirror 90 rotates, thus forming a horizontal image.
The beam reflected by the polygonal mirror 90 travels to a galvanometer 100. Here, the galvanometer 100 repeatedly moves up and down throughout a designated range of angles, thus forming a vertical image.
That is, the image is displayed on the screen 50 by scanning the laser beam through the combination of the rotation of the polygonal mirror 90 and the movement of the galvanometer 100 throughout the designated range of angles.
Since the above laser projection display unit uses the laser, it is possible to increase the visibility of colors, thereby being capable of displaying an image having colors close to natural colors. Further, it is possible to increase of contrast of colors, thereby increasing a picture quality.
Due to coherence, one of characteristics of the laser, the laser projection display unit generates interference of the laser on the screen, thereby generating speckles on the screen. These speckles deteriorate a picture quality, thus lowering the contrast and resolution of the image.
That is, the laser projection display unit displays an image having high visibility and excellent picture quality, but may deteriorate the contrast and resolution of the image due to the characteristics of the laser.